Topic Overview

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This topic will tell you about the early testing, diagnosis, and treatment of colorectal cancer. If you want to learn about colorectal cancer that has come back or has spread, see the topic Colorectal Cancer, Metastatic or Recurrent. If you want to learn about anal cancer, see the topic Anal Cancer.

What is colorectal cancer?

Colorectal cancer means that cells that aren't normal are growing in your colon or rectum. These cells grow together and form polyps. Over time, some polyps can turn into cancer.

This cancer is also called colon cancer or rectal cancer, depending on where the cancer is. It is the third most common cancer in the United States. And it occurs most often in people older than 50.

What causes colorectal cancer?

The exact cause of colorectal cancer is not known. Most cases begin as small growths, or polyps, inside the colon or rectum.

Colon polyps are very common. If they are found early, usually through routine screening tests, they can be removed before they turn into cancer.

What are the symptoms?

Colorectal cancer usually doesn't cause symptoms until after it has started to spread. See your doctor if you have any of these symptoms:

Pain in your belly

Blood in your stool or very dark stools

A change in your bowel habits, such as more frequent stools or a feeling that your bowels are not emptying completely

How is colorectal cancer diagnosed?

If your doctor thinks that you may have this cancer, you will need a test, called a colonoscopy (say "koh-luh-NAW-skuh-pee"), that lets the doctor see the inside of your entire colon and rectum. During this test, your doctor will remove polyps or take tissue samples from any areas that don't look normal. The tissue will be looked at under a microscope to see if it contains cancer.

Sometimes another test, such as a sigmoidoscopy (say "sig-moy-DAW-skuh-pee"), is used to diagnose colorectal cancer.

How is it treated?

How can you screen for colorectal cancer?

Screening tests can find or prevent many cases of colon and rectal cancer. They look for a certain disease or condition before any symptoms appear. Experts recommend routine colon cancer testing for everyone age 50 and older who has a normal risk for colon cancer. Your doctor may recommend getting tested more often or at a younger age if you have a higher risk. Talk to your doctor about when you should be tested.

The most common screening tests are:

Stool tests that check for signs of cancer, such as blood in the stool.

Sigmoidoscopy. A doctor uses a lighted scope to see the lower portion of the intestine. This is where most colon cancers grow. Doctors can also remove polyps during this test.

Colonoscopy. A doctor puts a long, flexible tube into your rectum and colon. The tube is usually linked to a video monitor similar to a TV screen. With this test, the doctor can see the entire large intestine.

Computed tomographic colonography (CTC), also called a virtual colonoscopy. A computer and X-rays make a detailed picture of the colon to help the doctor look for polyps.

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